JPH0150986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control signal generation circuit for a magnetic recording device, and it is possible to obtain control signals such as control pulses with a simple circuit such as a flip-flop, monomulti, gate circuit, etc., and is easy to integrate into an IC. Moreover, it is an object of the present invention to provide a control signal generation circuit that can be constructed at low cost.

When recording in a helical scan type small VTR, video signals are recorded on magnetic tape, and
A control pulse (30Hz) obtained by dividing the vertical synchronization signal (60Hz) of the video signal by 1/2 is recorded on a track separate from the video signal track. this is,
During reproduction, the phase of the sampling pulse obtained by reproducing the control pulse is compared with the trapezoidal wave signal obtained from the pulse from the reference frequency oscillator to obtain a phase comparison error signal, and this phase comparison error signal drives the capstan at a constant speed. This is to control the rotation.

On the other hand, during recording, from the vertical synchronization signal of the video signal,
Also, during playback, sampling pulses for drum motor control of 30 Hz are obtained from the reference frequency oscillator, and the phases of these sampling pulses and the trapezoidal wave signal obtained from the rotation pulse of the drum motor are compared to obtain a phase comparison error signal. The rotation of the drum motor is controlled at a constant speed using the phase comparison error signal.

Conventionally, there is a circuit shown in FIG. 1 as a circuit for obtaining control pulses and drum motor control sampling pulses from a vertical synchronization signal during recording. In FIG. 1, the video signal input to the input terminal 1 is separated into a synchronizing signal by the synchronizing signal separation circuit 2 (A in FIG. 2), and the vertical synchronizing signal a (60
Hz) and then supplied to the CR monomulti
The 30Hz control pulse e shown in Figure E is used. The control pulse e is supplied to the control head 5 and recorded on the magnetic tape 6, while
Pulse width d shown in Figure 2 D in CR monomulti 7
The sampling pulse generator 14 in the drum motor servo circuit 8 generates a sampling pulse synchronized with the fall of the signal d.

On the other hand, the rotation pulse from the drum motor 9 in the drum motor servo circuit 8 is converted into a 30Hz rectangular wave signal by a flip-flop 10, and then converted into a trapezoidal wave signal by a trapezoidal wave generation circuit 11, and then converted into a trapezoidal wave signal by a phase comparator circuit 12.
, where the sampling pulse generator 1
The phase is compared with the drum motor control sampling pulse from 4. Through this phase comparison, a phase comparison error signal is extracted and supplied to the drive circuit 13,
The drum motor 9 is controlled to rotate at a constant speed.

However, in this conventional circuit, the control pulse e
I used CR Mono Multi 4 as a circuit to obtain this, and also used it to generate sampling pulses for the drum servo.
Since CR Mono Multi 7 is used, two external components such as capacitor C and resistor R are required, making it difficult to integrate into an IC.

FIG. 3 shows a circuit diagram of another example of the conventional circuit. The video signal that has entered the input terminal 1 is separated from the synchronizing signal by the synchronizing signal separation circuit 2, converted into a vertical synchronizing signal a (60Hz) by the reduction filter 3, and then supplied to the digital pulse count monomulti 16. . In the pulse count monomulti 16, the number of pulses from the crystal generator is counted, and the vertical synchronization signal a
(60Hz) is frequency-divided and extracted into a 30Hz control pulse e shown in FIG. 2E. Other configurations and operations are similar to the circuit shown in the first diagram.

However, in this conventional circuit, the control pulse e
Since a digital pulse count monomulti 16 is used as the circuit for obtaining the , there is a drawback that it cannot be constructed at low cost.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

FIG. 4 shows a block system diagram of one embodiment of the control signal generation circuit of the magnetic recording device according to the present invention. In the figure, the same components as in FIG. 1 are given the same numbers and their explanations are omitted. do. In Figure 4, the vertical synchronization signal (60Hz) extracted from reduction filter 3 is
The CR monomulti 17 generates the pulse signal b shown in FIG. 2B, and the OR gate 18 and AND gate 1
9, supplied to flip-flop 20. signal b
is shown in FIG. 2C at the flip-flop 20.
The pulse signal c of 30 Hz is supplied to the OR gate 18 and the AND gate 19.

At OR gate 18, pulse signal b pulse signal c
The 30 Hz control pulse e shown in FIG. A drum motor control sampling pulse d of 30 Hz shown in FIG. 2D is taken out and supplied to the drum motor servo circuit 8.

As described above, the control signal generation circuit of the magnetic recording device according to the present invention includes a sync separation circuit that is supplied with a video signal and separates a sync signal from the video signal, and a sync separation circuit that separates a sync signal from the sync signal that is supplied from the sync separation circuit. a reduction filter that outputs a synchronization signal; a monomultiplier that outputs a pulse signal that has the same frequency as the vertical synchronization signal supplied from the reduction filter and has a pulse width wider than the pulse width of the vertical synchronization signal; A flip-flop outputs a frequency-divided signal obtained by dividing the pulse signal supplied from the mono-multi by 1/2, and a logical product is performed between the frequency-divided signal supplied from this flip-flop and the pulse signal supplied from the mono-multi. , an AND circuit that outputs a sampling pulse used to control the rotation of the rotary drum motor, and an AND circuit that outputs a sampling pulse used to control the rotation of the rotary drum motor, and performs the logical sum of the pulse signal supplied from the monomulti and the frequency-divided signal supplied from the flip-flop, and outputs the video signal. Because it is based on an OR circuit that outputs a control pulse obtained by dividing the vertical synchronization signal by 1/2,
Two pulse signals, a control pulse and a sampling pulse, can be created in one circuit, and the number of external components is halved compared to a conventional circuit using two CR monomultis, making it easier to integrate into an IC.
It has the advantage of being able to be constructed at a lower cost than conventional circuits using digital, pulse counting monomultis.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an example of a conventional circuit, FIGS. 2A to 2E are signal waveform diagrams for explaining the operation of the conventional circuit and the circuit of the present invention, and FIG. FIG. 4 is a block system diagram of an embodiment of the circuit of the present invention. DESCRIPTION OF SYMBOLS 1... Video signal input terminal, 2... Synchronous signal separation circuit, 3... Reduction filter, 5... Control head, 6... Magnetic tape, 8... Drum motor servo circuit, 17... Mono multi, 18... …or gate, 19…and gate, 20…flipflop.

Claims (1)

[Claims] 1. A sync separation circuit to which a video signal is supplied and which separates a sync signal from the video signal; a low-pass filter that outputs a vertical sync signal from the sync signal supplied from the sync separation circuit; a monomulti that outputs a pulse signal having the same frequency as the vertical synchronization signal supplied from a low-pass filter and a pulse width wider than the pulse width of the vertical synchronization signal, and a pulse signal supplied from the monomulti 1/
A flip-flop outputs a frequency-divided signal whose frequency is divided by two, and the frequency-divided signal supplied from this flip-flop is ANDed with the pulse signal supplied from the monomulti to control the rotation of the rotary drum motor. An AND circuit that outputs the sampling pulse to be used, performs a logical sum of the pulse signal supplied from the monomulti and the frequency-divided signal supplied from the flip-flop, and divides the vertical synchronization signal of the video signal by 1/2.
A control signal generation circuit for a magnetic recording device, comprising an OR circuit that outputs a control pulse obtained by dividing the frequency by two.